U.S. patent application number 11/746304 was filed with the patent office on 2007-12-27 for image forming method.
This patent application is currently assigned to KONICA MINOLTA BUSINESS TECHNOLOGIES, INC.. Invention is credited to Masahiro ANNO, Tomoko MINE, Masahiko NAKAMURA, Kenichi ONAKA, Kaori SOEDA, Eiichi YOSHIDA.
Application Number | 20070298338 11/746304 |
Document ID | / |
Family ID | 38510477 |
Filed Date | 2007-12-27 |
United States Patent
Application |
20070298338 |
Kind Code |
A1 |
NAKAMURA; Masahiko ; et
al. |
December 27, 2007 |
IMAGE FORMING METHOD
Abstract
An electrophotographic image forming method is disclosed. In the
method electrostatic latent image is developed by a non-magnetic
single-component developing system, in which a non-magnetic
single-component developer is conveyed by a developer carrying
member, the developer carrying member is contacted with a developer
layer regulation member for regulating an amount of the developer
at the surface of the developer carrying member, and a binder resin
of the developer comprises a vinyl polymer having an acid value of
from about 5 to about 30 and a ratio of hydroxyl group value/acid
values from about 0.3 to about 0.8.
Inventors: |
NAKAMURA; Masahiko; (Tokyo,
JP) ; ANNO; Masahiro; (Tokyo, JP) ; SOEDA;
Kaori; (Tokyo, JP) ; MINE; Tomoko; (Tokyo,
JP) ; ONAKA; Kenichi; (Tokyo, JP) ; YOSHIDA;
Eiichi; (Tokyo, JP) |
Correspondence
Address: |
LUCAS & MERCANTI, LLP
475 PARK AVENUE SOUTH, 15TH FLOOR
NEW YORK
NY
10016
US
|
Assignee: |
KONICA MINOLTA BUSINESS
TECHNOLOGIES, INC.
Tokyo
JP
|
Family ID: |
38510477 |
Appl. No.: |
11/746304 |
Filed: |
May 9, 2007 |
Current U.S.
Class: |
430/48 |
Current CPC
Class: |
G03G 2215/0617 20130101;
G03G 9/08722 20130101; G03G 9/08795 20130101; G03G 9/0804 20130101;
G03G 9/0874 20130101; G03G 2215/0619 20130101; G03G 9/08791
20130101; G03G 9/08711 20130101; G03G 9/08797 20130101; G03G
9/08724 20130101 |
Class at
Publication: |
430/48 |
International
Class: |
G03G 13/04 20060101
G03G013/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2006 |
JP |
2006-171145 |
Claims
1. An image forming method comprising steps of; forming an
electrostatic latent image on an electrostatic latent image
carrying member, developing the electrostatic latent image by a
non-magnetic single-component developing system, in which a
non-magnetic single-component developer is conveyed by a developer
carrying member, and the developer carrying member is contacted
with a developer layer regulation member for regulating an amount
of the developer at the surface of the developer carrying member,
wherein a binder resin of the developer comprises a vinyl polymer
having an acid value of from 5 to 30 and a ratio of hydroxyl group
value/acid value is from 0.3 to 0.8.
2. The image forming method of claim 1 wherein a hydroxyl group
value of the vinyl polymer is from 1.5 to 24.
3. The image forming method of claim 1 wherein the vinyl polymer
comprises a hydroxyl group and an acid group in a side chain.
4. The image forming method of claim 3 wherein the vinyl polymer is
derived from a monomer having an acid group and a monomer having a
hydroxyl group as polymerizable monomers to constitute the vinyl
polymer.
5. The image forming method of claim 4 wherein the acid group is at
least one of a carboxyl group, a sulfonic acid group and a
phosphoric acid group.
6. The image forming method of claim 5 wherein the monomer having
an acid group includes at least one of acrylic acid, methacrylic
acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid,
monoalkyl maleate, monoalkyl itaconate, styrenesulfonic acid,
allylsulfosuccinic acid, 2-acrylamide-2-methylpropanesulfonic acid,
acidphosphoxyethyl methacrylate and 3-chloro-2-acidphophoxypropyl
methacrylate.
7. The image forming method of claim 4, wherein the monomer having
a hydroxyl group includes at least one of hydroxyalkyl acrylate and
hydroxyalkyl methacrylate.
8. The image forming method of claim 4 wherein the monomer having a
hydroxyl group includes at least of 2-hydroxyethyl acrylate,
2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate,
2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate,
2-hydroxybutyl methacrylate, 4-hydroxybutyl acrylate and
4-hydroxybutyl methacrylate.
9. The image forming method of claim 4 wherein the monomer having a
hydroxyl group is vinyl ether having a hydroxyl group.
10. The image forming method of claim 9 wherein the monomer having
a hydroxyl group includes at least one of 2-hydroxyethylvinylether,
4-hydroxybutylvinylether and 6-hydroxyhexyl vinylether.
11. The image forming method of claim 1 wherein a glass transition
point of the binder resin is from 20 to 90.degree. C.
12. The image forming method of claim 1 wherein a softening point
of the binder resin is from 80 to 220.degree. C.
13. The image forming method of claim 1 wherein the developer layer
regulation member is contacted with the developer carrying member
at a pressure of from 0.1 N/cm to 5.0 N/cm.
14. The image forming method of claim 1 wherein the developer layer
regulation member is contacted with the developer carrying member
at a pressure of from 0.2 to 4.0 N/cm.
15. The image forming method of claim 13 wherein the developer
layer regulation member is a urethane rubber or a metal plate.
16. The image forming method of claim 15 wherein the developer
layer regulation member is a steel elastic blade.
17. The image forming method of claim 1, wherein the developer is
formed by coagulating a resin and a colorant in an aqueous medium.
Description
[0001] This application is based on Japanese Patent Application No.
2006-171145 filed on Jun. 21, 2006, in Japanese Patent Office, the
entire content of which is hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to an electrophotographic
image forming method using a non-magnetic single-component
developing system.
TECHNICAL BACKGROUND
[0003] As the non-magnetic single-component developing system, for
example, methods described in Japanese Patent Laid Open to Public
Publication (JP-A) Nos. 63-212946, 63-271374 and Japanese Patent
Examined Publication (JP-B) No. 2774534 have been known. In this
system, an electrostatic latent image is developed by supplying a
thin layer of a non-magnetic developer onto the surface of a
electrostatic latent image forming member by a developing apparatus
having a developer carrying member, a toner layer regulation member
and a toner supply assisting member in which the toner supply
assisting member and the developer carrying member, and toner layer
regulation member and the developer carrying member are
respectively contacted with together to form the developer thin
layer. In such the method, the non-magnetic toner is charged by
friction electrification of the non-magnetic developer with
developer carrying member and the toner layer regulation
member.
[0004] Color electrophotographic apparatuses have a merit such as
that the developing apparatus can be made compact and are widely
utilized at desk side of offices, in small offices, SOHO and
domestic houses. In the non-magnetic single-component developing
system, the toner particles are electrically charged by passing
through the gap between the developer carrying member and the toner
layer regulation member arranged to be contacted with the toner
layer regulation member. The toner particles receive stress on the
occasion of passing through the gap between the developer carrying
member and the toner regulation member. The mechanical strength of
the toner particles is held by raising the softening point thereof
by controlling the molecular weight thereof or giving crosslinked
structure so as to prevent the crushing of the toner particles by
the stress. As a result of that, the fixing temperature is raised
and electric consumption is increased so that the load onto the use
in the small offices, SOHO and domestic house is increased. Under
such the conditions, a technique for dispersing organic polymer
fine particles having high softening point and a particle diameter
of not more than 0.5 .mu.m, cf. Patent Document 1 for example, and
that by which filler particles are dispersed in a thermoplastic
layer covering the nucleus particles mainly composed of
thermoplastic resin and colorant, cf. Patent Document 2 for
example, have been known. However, such the toner particles do not
satisfy the fixing ability at low temperature and anti-crushing
ability.
[0005] Patent Document 1: JP-A 2-1869
[0006] Patent Document 2: JP-A 7-36213
SUMMARY
[0007] An object of the invention is to provide an image forming
method using non-magnetic single-component developing system by
which an image having low temperature fixing ability and high
quality image can be stably obtained.
[0008] Embodiments of this invention are described.
[0009] 1. An image forming method by which an electrostatic latent
image formed on a electrostatic latent image carrying member is
developed by a non-magnetic single-component developing system by a
developer conveyed by a developer carrying member contacted with a
developer layer regulation member for regulating the amount of the
developer at the surface of the developer carrying member, wherein
binder resin of the developer is vinyl type polymer having an acid
value of from 5 to 30 and a ratio of hydroxyl group value/acid
value is from 0.3 to 0.8.
[0010] 2. The image forming method of the above item 1, wherein the
developer is formed by coagulating the resin and a colorant in an
aqueous medium.
BRIEF DESCRIPTION OF DRAWING
[0011] FIG. 1 shows a schematic cross section of an example of
developing apparatus to be used in the image forming method of the
invention.
[0012] The image forming method using the non-magnetic
single-component developing system can be provided by the
invention, by which an image having low temperature fixing ability
and high quality image can be stably obtained.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] In the image forming method of the invention, an
electrostatic latent image formed on the electrostatic latent image
carrying member is developed by the non-magnetic single-component
developing system. In this system a non-magnetic single-component
developer is conveyed by a developer carrying member, and the
developer carrying member is contacted with a developer layer
regulation member for regulating an amount of the developer at the
surface of the developer carrying member, and a binder resin of the
developer is vinyl type polymer having an acid value of from 5 to
30 and a ratio of hydroxyl group value/acid value is from 0.3 to
0.8. The hydroxyl group value is preferably from 1.5 to 24.
[0014] The binder resin is composed of vinyl based polymer and does
not include a polyester based polymer. The developer having
sufficient mechanical strength even though the softening point
thereof is lower than usual developers can be obtained by
controlling the hydroxyl group value and acid value of the vinyl
based polymer used as the binder resin.
[0015] In the invention, the developer is a colored particle
comprising the resin and the colorant which are externally treated
by an additive such as hydrophobic silica.
[0016] In concrete, the softening point of the developer can be
lowered while holding the mechanical strength thereof at room
temperature by utilizing the hydrogen bond between the hydroxyl
group and the acidic group. The hydrogen bond physically links the
acidic group and the hydroxyl group of molecular chains at room
temperature so as to raise the mechanical strength at room
temperature. The kinks are easily broken when the resin is heated.
The toner can be fixed at a temperature lower than that in the
usual method while maintaining the mechanical strength by
positively introducing the hydrogen bonds to the side chain of the
vinyl type polymer resin. The vinyl type polymer resin comprises
hydroxyl groups and acid groups in side chain of the polymer.
[0017] When the acid value is less than 5, formation of the
hydrogen bonds is insufficient and contribution on the mechanical
strength is small and when the acid value exceeds 30, the moisture
amount absorbed by the developer is increased and sufficient charge
cannot be obtained so as to cause image defects such as fogging and
transfer lacking. In the case of that the ratio of hydroxyl group
value/acid value is less than 0.3, the hydrogen bonds are
insufficiently formed and contribution on the mechanical strength
is small. When the ratio of hydroxyl group value/acid value in the
binder resin exceeds 0.8, the acid groups having negative polarity
are shortened and sufficient negative chargeability cannot be
obtained.
[0018] The acid value and the ratio of hydroxyl group value/acid
value can be controlled by controlling the using amount of an
acidic monomer, a monomer having hydroxyl group and a
polymerization initiator having a hydroxyl group. The acid value is
determined according to the acid value testing method of JIS K0070.
As the solvent, a mixture of tetrahydrofuran and isopropyl alcohol
in a volume ratio of 1:1 is used and the acid value is measured by
a potentiometric titration method. The hydroxyl group value is
determined by a potentiometric titration method according to the
hydroxyl group value testing method of JIS K0070.
[0019] The colored particle according to the invention can be
produced by a suspension polymerization or an emulsion
polymerization method in which a monomer is emulsion polymerized in
a liquid containing an emulsion of necessary additive to form fine
polymerized particles and then the particles are associated by
adding an organic solvent or an aggregation agent. A method in
which a dispersion of a component necessary for constituting the
colored particle such as a parting agent and a colorant is mixed
with the above emulsified polymer particles on the occasion of the
association of the particles and a method in which the color
particle constituting component such as the parting agent and the
colorant is dispersed in the monomer and then polymerized are
applicable. The association is defined as fusion of several numbers
of resin particle and the colorant particles.
[0020] In the invention, the aqueous medium is a medium containing
at least 50% by weight of water.
[0021] The constituting materials such as the parting agent, a
charge controlling agent and the polymerization initiator are added
into the polymerizable monomer and dissolved or dispersed them by a
dispersing means such as a homogenizer, a sand mill, a sand grinder
and a ultrasonic dispersing machine. The polymerizable monomer in
which the constitution materials are dissolved or dispersed is
dispersed into the form of oil droplet each having a sized desired
for the colored particle in the aqueous medium containing a
dispersion stabilizer by a homo-mixer or a homogenizer. After that,
the resultant dispersion is transferred into a reacting vessel
having a stirring mechanism having the later-mentioned stirring
wing and heated for accelerating the polymerization reaction. After
the completion of the reaction, the dispersion stabilizer is
removed and the polymerized particles are filtered, washed and
dried to prepare the colored particles of the invention.
[0022] Example of a method to produce the toner of the present
invention includes a method in which resin particles are prepared
upon associating or fusing with each other in an aqueous medium.
This method is not particularly limited, and other methods may be
listed which are disclosed in, for example, Japanese Patent
Publication Open to Public Inspection Nos. 5-265252, 6-329947, and
9-15904.
[0023] The toner of the present invention is prepared employing a
method in which a plurality of dispersion particles of the
constitution materials comprised of resin particles, colorants and
the like, or of fine particles comprised of resins, colorants, and
the like, are associated, in which in particular, after dispersing
these into water employing an emulsifier, the resulting dispersion
is salted out by adding a coagulant in an amount of more than the
critical coagulation concentration; at the same time, while forming
fused particles upon heating the formed polymer at least to the
glass transition temperature of the polymer, so as to fuse with
each other, the particle diameter is increased; when growing the
particle diameter to a desired diameter, a large amount of water is
added to halt the growth of the diameter; the particle surface is
then smoothed through heating and stirring, whereby the shape is
controlled; and the resulting particles are heat dried in a fluid
state while suspended in a water comprising state. Further, herein,
organic solvents which are infinitely soluble in water may be added
at the same time, together with a coagulating agent.
[0024] Employed polymerizable monomers to constitute a resin
include styrenes or styrene derivatives such as styrene,
o-methylstyrene, m-methylstyrene, p-methylstyrene,
.alpha.-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene,
p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert
butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene,
p-n-decylstyrene, p-n-dodecylstyrene; methacrylic acid ester
derivatives such as methyl methacrylate, ethyl methacrylate,
n-butyl methacrylate, isopropyl methacrylate, isobutyl
methacrylate, t-butyl methacrylate, n-octyl methacrylate,
2-ethylhexyl methacrylate, stearyl methacrylate, lauryl
methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate,
dimethylaminoethyl methacrylate, and the like; acrylic acid ester
derivatives such as methyl acrylate, ethyl acrylate, isopropyl
acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate,
n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl
acrylate, phenyl acrylate, and the like; olefins such as ethylene,
propylene, isobutylene, and the like; halogen based vinyls such as
vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride,
vinylidene fluoride, and the like; vinyl esters such as vinyl
propionate, vinyl acetate, vinyl benzoate, and the like; vinyl
ethers such as vinyl methyl ether, vinyl ethyl ether, and the like;
vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone,
vinyl hexyl ketone, and the like; N-vinyl compounds such as
N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidone, and the like;
vinyl compounds such as vinylnaphthalene, vinylpyridine, and the
like; acrylic acid or methacrylic acid derivatives such as
acrylonitrile, methacrylonitrile, acrylamide and the like. These
vinyl based monomers may be employed individually or in
combination.
[0025] An acid monomer is used as polymerizable monomers, which
constitute a resin in combination with the afore-mentioned
polymerizable monomer. The example include those having a
substituent such as a carboxyl group, a sulfonic acid group, a
phosphoric acid group, and the like in the acid monomer. Listed as
specific examples are acrylic acid, methacrylic acid, maleic acid,
itaconic acid, cinnamic acid, fumaric acid, monoalkyl maleate,
monoalkyl itaconate, styrenesulfonic acid, allylsulfosuccinic acid,
2-acrylamide-2-methylpropanesulfonic acid, acidphosphoxyethyl
methacrylate, 3-chloro-2-acidphophoxypropyl methacrylate, and the
like.
[0026] For the purpose of introducing a hydroxyl group,
polymerizable monomers including various hydroxyalkyl
(meth)acrylates such as such as 2-hydroxyethyl (meth)acrylate,
2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and
4-hydroxybutyl (meth)acrylate, or various vinyl ethers such as
2-hydroxyethylvinylether, 4-hydroxybutylvinylether and
6-hydroxyhexyl vinylether
[0027] Polymerization initiator including hydrogen peroxide or an
organic peroxide having a hydroxyl group in a molecule, may be
employed for the same purpose, if necessary.
[0028] Further, the resin may be modified so as to have a
cross-linking structure, employing multifunctional vinyls such as
divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol
diacrylate, diethylene glycol dimethacrylate, diethylene glycol
diacrylate, triethylene glycol dimethacrylate, triethylene glycol
diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol
diacrylate, and the like.
[0029] These polymerizable monomers may undergo polymerization
employing a radical polymerization initiator. In such cases,
oil-soluble polymerization initiators may be employed in a
suspension polymerization method. Such oil-soluble polymerization
initiators include azo based or diazo based polymerization
initiators such as 2,2'-azobis-(2,4-dimethylvaleronitrile,
2,2'-azobisisobutyronitrile,
1,1'-azobis(cyclohexane-1-carbonitrile),
2,2-azobis-4-methoxy-2,4-dimethylvaleronitrile,
azobisisobutyronitrile, and the like; and peroxide based
polymerization initiators and polymer initiators having a peroxide
in the side chain such as benzoyl peroxide, methyl ethyl ketone
peroxide, di-isopropylperoxycarbonate, cumenehydroperoxide,
t-butylhydroperoxide, di-t-butylperoxide, dicumylperoxide,
2,4-dichlorobenzoyloxide, lauroylperoxide,
2,2-bis-(4,4-t-butylperoxycyclohexyl)propane,
tris-(t-butylperoxy)triazine, and the like.
[0030] Further, when the emulsion polymerization method is
employed, water-soluble radical polymerization initiators may be
employed. Water-soluble polymerization initiators include
persulfates such as potassium persulfate, ammonium persulfate, and
the like, azobisaminodipropane acetic acid salts,
azobiscyanovaleric acid and salts thereof, hydrogen peroxide, and
the like.
[0031] Listed as dispersion stabilizers may be tricalcium
phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate,
calcium carbonate, magnesium sulfate, calcium hydroxide, magnesium
hydroxide, aluminum hydroxide, calcium metasilicate, calcium
sulfate, barium sulfate, bentonite, silica, alumina, and the like.
Further, also employed as dispersion stabilizers may be those which
are generally employed as surface active agents such as polyvinyl
alcohol, gelatin, methyl cellulose, sodium dodecybenzenesulfonate,
ethylene oxide additives, higher alcohol sodium sulfate, and the
like.
[0032] Preferred as the binder resins are those having a glass
transition point of 20 to 90.degree. C., as well as a softening
point of 80 to 220.degree. C. The glass transition point is a value
measured by a differential calorimetric method, while the softening
point can be measured by an elevated type flow tester. Further,
these resins preferably have a number average molecular weight (Mn)
of 1,000 to 100,000, as well as a weight average molecular weight
(Mw) of 2,000 to 1,000,000, which are measured by gel permeation
chromatography. Further, as a molecular weight distribution, the
Mw/Mn is preferably between 1.5 and 100, and is most preferably
between 1.8 and 70.
[0033] The employed coagulating agents are not particularly
limited, however those selected from metal salts are more suitable.
Specific examples include salts of univalent metals such as alkali
metals, for example, sodium, potassium, lithium and the like;
alkali earth metal salts of divalent metals such as calcium,
magnesium, and the like; salts of divalent metals such as
manganese, copper, and the like; and salts of trivalent metals such
as iron, aluminum, and the like. Listed as specific salts can be
sodium chloride, potassium chloride, lithium chloride, calcium
chloride, zinc chloride, copper sulfate, magnesium sulfate,
manganese sulfate, and the like. These may be employed in
combination.
[0034] These coagulants are preferably added in an amount exceeding
the critical coagulation concentration. The critical coagulation
concentration as described herein is an index on the stability of
an aqueous dispersion, and concentration at which coagulation is
formed by the addition of a coagulant. The critical coagulation
concentration varies greatly depending on the emulsified components
and dispersing agents themselves. For example, the critical
coagulation concentration is described in Seize Okamura, et al.
"Kobunshi Kagaku (Polymer Chemistry)", edited by Nihon Kobunshi
Gakkai, whereby detailed critical coagulation concentration data
can be obtained. Furthermore, as another method, zeta (zeta)
potentials of a specified particle dispersion are measured upon
adding a desired salt to the particle dispersion, while changing
the salt concentration, and said salt concentration which varies
the zeta potential can be obtained as the critical coagulation
concentration.
[0035] The added amount of the coagulant of the present invention
is acceptable if it exceeds the critical coagulation concentration.
However, the addition amount is preferably at least 1.2 times of
the critical coagulation concentration, and is more preferably at
least 1.5 times.
[0036] A solvent which is infinitely soluble denotes a solvent
which is infinitely soluble in water and as such solvents, those
which do not dissolve the resin formed in the present invention are
selected. Specifically, cited are alcohols such as methanol,
ethanol, propanol, isopropanol, t-butanol, methoxyethanol,
butoxyethanol, and the like, nitrites such as acetonitrile, and
ethers such as dioxane. In particular, ethanol, propanol and
isopropanol are preferred.
[0037] The added amount of such solvents which are infinitely
soluble is preferably between 1 and 100 percent by volume of the
polymer containing dispersion to which the coagulant is added.
[0038] Further, in order to make all particles of a uniform shape,
after preparing colored particles and filtering them, the resulting
slurry, in which water is present in an amount of at least 10
percent by weight of the particles, is preferably subjected to
fluidized drying. At the time, those which comprise a polar group
in the polymer are particularly preferred. As the reason, it is
assumed that since existing water somewhat exhibits swelling effect
for the polymer comprising the polar group, making particles of a
uniform shape tends to be particularly easily carried out.
[0039] The toner of the present invention comprises at least a
resin and a colorant, but may as well comprise a releasing agent
which works as a fixing property improving agent, a charge control
agent, and the like. Further, external additives comprised of fine
inorganic particles, fine organic particles, and the like may be
added to toner particles which are mainly comprised of the
above-mentioned resin and colorant.
[0040] Optionally employed as colorants in the invention, which are
employed in the toner of the present invention, may be carbon
blacks, magnetic materials, dyes, pigments, and the like. Employed
as said carbon blacks are channel black, furnace black, acetylene
black, thermal black, lamp black, and the like. Employed as
magnetic materials may be ferromagnetic metals such as iron,
nickel, cobalt, and the like, as well as alloys which do not
comprise ferromagnetic metals and are subjected to thermal
treatment to exhibit ferromagnetism, such types of alloys being
called Heusler's alloys, being for example,
manganese-copper-aluminum, manganese-copper-tin and the like, and
also chromium dioxide, and the like.
[0041] Employed as dyes can be C.I. Solvent Red 1, Solvent Red 49,
Solvent Red 52, Solvent Red 58, Solvent Red 63, Solvent Red 111,
and Solvent Red 122, C.I. Solvent Yellow 19, Solvent Yellow 44,
Solvent Yellow 77, Solvent Yellow 79, Solvent Yellow 81, Solvent
Yellow 82, Solvent Yellow 93, Solvent Yellow 98, Solvent Yellow
103, Solvent Yellow 104, Solvent Yellow 112, and Solvent Yellow
162; C.I. Solvent Blue 25, Solvent Blue 36, Solvent Blue 60,
Solvent Blue 70, Solvent Blue 93, and Solvent Blue 95, and the
like. Furthermore, these mixtures may be employed. Employed as
pigments may be C.I. Pigment Red 5, Pigment Red 48:1, Pigment Red
53:1, Pigment Red 57:1, Pigment Red 122, Pigment Red 139, Pigment
Red 144, Pigment Red 149, Pigment Red 166, Pigment Red 177, Pigment
Red 178, and Pigment Red 222; C.I. Pigment Orange 31, and Pigment
Orange 43; C.I. Pigment Yellow 14, Pigment Yellow 17, Pigment
Yellow 93, Pigment Yellow 94, and Pigment Yellow 138; and C.I.
Pigment Green 7; and C.I. Pigment Blue 15:3, and Pigment Blue 60;
and the like. These mixtures may also be employed. The average
primary particle diameter varies depending on type, generally,
however it is preferably between about 10 and about 200 nm.
[0042] The colorants may be added employing ant of several common
methods, in which colorants are added during which polymer
particles prepared by an emulsion polymerization method are
coagulated by adding a coagulant and the polymer is tinted; during
polymerizing of said monomers, a colorant is added and the
resulting mixture is polymerized to form tinted particles; and the
like. Further, when the colorant is added during polymer
preparation, it is preferably subjected to surface treatment
employing a coupling agent and the like, which is employed so that
radical polymerization is not hindered.
[0043] Further, added as fixing property enhancing agents may be
low molecular weight polypropylene (having a number average
molecular weight of 1,500 to 9,000) or low molecular weight
polyethylene.
[0044] Charge control agents may also be employed, which are known
in the art, and can be dispersed into water. Specifically listed
are Nigrosine based dyes, metal salts of naphthenic acid or higher
fatty acids, alkoxylated amines, quaternary ammonium salts, azo
based metal complexes, salicylic acid metal salts or metal
complexes thereof, and such.
[0045] Further, these charge control agents and fixing property
enhancing agents are preferably in a dispersed state, and the
number average primary particle diameter is adjusted from about 10
to about 500 nm.
[0046] In a suspension polymerization method in which a
composition, prepared by dispersing or dissolving toner
constitution components such as a colorant and the like in
polymerizable monomers, is suspended in a water based medium, and
then undergoes polymerization to obtain the toner, the shape of
toner particles may be controlled by controlling the flow of the
medium in a reaction vessel in which the reaction is carried out.
Namely, when many toner particles having a shape coefficient of at
least 1.2 are formed, the flow in the reaction vessel is regulated
to a turbulent one; polymerization proceeds; and when oil droplets
suspended in the water based medium are gradually polymerized and
oil droplets become soft particles, particle union is accelerated
due to collisions of particles resulting in particles which are not
stable in shape. Further, when spherical toner particles having a
shape coefficient of not more than 1.2 are formed, the flow of the
medium in said reaction vessel is regulated to a laminar flow to
result in spherical particles upon minimal collisions between
particles. Employing such methods, it is possible to control the
toner shape distribution within the range specified by the present
invention.
[0047] The developing apparatus to be used in the image forming
method of the invention is described below. The developing
apparatus to be used in the invention has a developer carrying
member, a toner layer regulation member, and a developer supply
assisting means and a developer carrying member and the developer
layer regulation member and the developer carrying member are
respectively contacted with together. In the developing system, the
latent image is developed by supplying the thin layer of the
non-magnetic developer formed by the apparatus.
[0048] The developer carrying member supplies the non-magnetic
single-component developer onto the electrostatic latent image
forming member, which is preferably elastic for obtaining a
sufficient developing area by the elasticity in the state of
contacted with the electrostatic latent image forming member.
[0049] In the invention, a roller of urethane rubber or silicone
rubber, and a nickel endless belt-shaped member including a sponge
roller therein are usable for the developer carrying member.
[0050] The developer layer regulation member has a function of
uniformly providing the developer on the developer carrying member
and giving frictional charge. An elastic material such as urethane
rubber or a metal plate is used as the developer layer regulation
means. Such the member is contacted to the developer carrying
member to form the thin layer of the developer on the developer
carrying member. The thin layer of the developer is a layer formed
by piling 10 layers at the maximum, preferably not more than 5
layers, of the developer particles. The developer layer regulation
member is preferably contacted with the developer carrying member
at a pressure of from 0.1 N/cm to 5.0 N/cm, and more preferably
from 0.2 to 4.0 N/cm. When the pressure is less than 0.1 N/cm, the
transportation of the developer becomes non-uniform so that
non-uniformity of the image and a problem of occurrence of white
line defect on the image tend to be caused. The developer carrying
member preferably has a diameter of from 10 to 50 mm.
[0051] The developer supply assisting member is a unit for stably
supplying the developer to the developer carrying member. As such
the supply assisting member, a water wheel-shaped roller having a
stirring wing or a sponge roller can be used. The supply assisting
member preferably has a diameter of from 0.2 to 1.5 times of the
diameter of the developer carrying member. When the diameter is too
small, the supply of the developer becomes insufficient and the
diameter excessively large causes excessive supply of the
developer. In both of the cases, the supply of the developer
becomes instable and line-shaped image defects tend to be
caused.
[0052] The electrostatic latent image carrying member is typically
an electrophotographic photoreceptor. In concrete, an inorganic
photoreceptor such as a selenium, arsenic-selenium and amorphous
silicon photoreceptor and an organic photoreceptor can be cited.
The organic photoreceptor is particularly preferred and that having
a multi-layered structure including a charge transfer layer and a
charge generation layer is preferable.
[0053] FIG. 1 shows a schematic cross section of an example of the
developing apparatus for the image forming method of the
invention.
[0054] In FIG. 1, a non-magnetic single-component developer 16
contained in a developer tank 17 is coercively conveyed and
supplied onto a sponge roller 14 as the developer supply assisting
member by a stirring wing 15 as the developer supply assisting
member. The developer thus supplied on the sponge roller 14 is
conveyed onto a developer carrying member 12 as the developer
carrying member by rotation of the sponge roller in the arrow
direction. The developer is electrostatically and physically
absorbed on the surface of the developer carrying member by the
friction with the developer carrying member 12. The developer thus
absorbed on the developer carrying member 12 is formed into a
uniform thin layer and frictionally electrified by rotation of the
developer carrying member 12 in the arrow direction and a steel
elastic blade 13 as the developer layer regulation member. After
that, the developer thin layer formed on the developer carrying
member 12 is contacted or neared to the surface of an
electrophotographic photoreceptor drum 11 as the electrostatic
latent image carrying member for developing the latent image.
[0055] As a fixing method preferably applied in the invention, a
contact heating method can be cited. The contact heating method
includes a heat-pressing fixing method, particularly the
heat-pressing fixing method using a heating roller or that using a
rotatable pressing member including a heater fixed therein.
[0056] In the heating roller fixing method, the apparatus is
frequently composed of an upper roller composed of a metal cylinder
of iron or aluminum covered with tetrafluoroethylene or
poly(tetrafluoroethylene-perfluoroalkoxy vinyl ether) which has a
heat source therein and a lower roller composed of a material such
as silicone rubber. The typical example of the heat source is a
line-shaped heater capable of heating the upper roller by a surface
temperature of from 120 to 200.degree. C. In the fixing portion,
pressure is applied between the upper and the lower rollers to form
a nip by deformation of the lower roller. The width of the nip is
from 1 to 10 mm and preferably from 1.5 to 7 mm. The line speed of
fixation is preferably from 40 to 600 mm/sec. When the nip is too
narrow, heat cannot be uniformly applied to the developer so as to
cause non-uniform fixing. Besides, the excessively wide nip
accelerates the fusion of the developer and causes a problem of
excessive occurrence of off-set.
[0057] A fixing apparatus cleaning means may be provided. As such
the method, a method by supplying silicone oil to the upper roller
of the film or that for cleaning by a pat, roller or web
impregnated with silicone oil are applicable.
[0058] The method for fixing by a rotating pressing member
including a heating member fixed therein is described bellow.
[0059] In such the fixing system, the fixation is carried out by
pressing and heating by the fixedly provided heating member and the
pressing member faced and pressed to the heating member by which
the recording material is contacted to the heating member through
film.
[0060] In the heat-pressing fixing apparatus, the heating member
has a line-shaped heater provided in the direction crossing at a
right angle to the conveying direction of the recording material,
and the thermal capacity thereof is smaller than that of a usual
heating roller, and the highest temperature of the heater is within
the range of from 100 to 300.degree. C.
[0061] The heat-pressing fixation is a fixing method by pressing
the non-fixed developer image to the heating source such as a
usually applied method in which a recording material carrying the
non-fixed developer image is passed between a heating member and a
pressing member. The fixing speed can be raised by such the method
since heat can be rapidly applied. However, the fixing temperature
is difficultly controlled and the developer off-set tends to be
caused by developer remaining at the portion to be directly touched
to the non-fixed developer such as the surface of the heating
member and a problem of winding the recording material on the
fixing roller tends to be caused.
EXAMPLES
[0062] The following examples will further illustrate the
invention. However, the embodiment of the invention is not limited
to the examples.
Example 1
(Preparation of Colored Particle C1)
[0063] (1) Preparation of Latex 1HML
[0064] 1) Preparation of Core Particle (The First Step of
Polymerization): Preparation of Latex 1H
[0065] Into a 5,000 ml separable flask, to which a stirring device,
a thermal sensor, a cooling pipe and a nitrogen gas introducing
device are attached, a surfactant solution (aqueous medium)
composed of 3,010 g of deionized water and 7.08 g of an anionic
surfactant, sodium lauryl sulfate, dissolved in the deionized water
was charged and heated by 80.degree. C. while stirring at a
stirring rate of 230 rpm.
[0066] To the surfactant solution, an initiator solution composed
of 400 g of deionized water and 9.2 g of a polymerization initiator
(potassium persulfate: KPS) dissolved therein was added and then
the temperature was adjusted to 75.degree. C. After that, a mixture
of monomers composed of 74.7 g of styrene, 22.0 g of n-butyl
acrylate, 0.88 g of acrylic acid and 0.50 g of
2-hydroxyethylacrylate was dropped spending 1 hour. The system was
heated and stirred at 75.degree. C. for 2 hours to perform the
polymerization (the first step polymerization) to form latex
(dispersion of resin particles composed of high molecular weight
resin). The latex was referred to as Latex 1H. 2) Formation of
Intermediate Layer (Second Step of Polymerization): Preparation of
Latex 1HM
[0067] A monomer solution was prepared by adding 98.0 g of compound
represented by the following Formula, to a monomer mixture liquid
composed of 104.9 g of styrene, 30.2 g of n-butyl acrylate, 1.24 g
of acrylic acid, 0.70 g of 2-hydroxyethylacrylate and 5.6 g of
n-octyl-3-mercaptopropionic acid ester at 90.degree. C. in a flask
to which a stirring device was attached.
##STR00001##
[0068] On the other hand, a surfactant solution composed of 2,700
ml of deionized water and, dissolved therein, 1.6 g of an anionic
surfactant, sodium lauryl sulfate, was heated up to 98.degree. C.
and 28 g in terms of solid ingredient of Latex 1H which is a
dispersion of the core particles was added to the surfactant
solution. Then the above prepared monomer solution was mixed and
dispersed for 8 hours in the above resulted liquid by a mechanical
dispersing apparatus having a circulation pass CLEARMIX
manufactured by M Technique Co., Ltd., to prepare a dispersion
(emulsion) containing emulsified particles (oil droplets).
[0069] After that, an initiator liquid composed of 240 ml of
deionized water and 5.1 g of the polymerization initiator (KPS)
dissolved therein, and 750 ml of deionized water was added to the
dispersion liquid (emulsion), the system was heated and stirred for
12 hours at 98.degree. C. to perform polymerization (second step
polymerization). Thus latex was obtained which was referred to as
Latex 1HM, which is a dispersion liquid of composite resin
particles having a structure that the surface of resin particles
composed of the high molecular weight resin is covered with a resin
having medium molecular weight.
[0070] 3) Preparation of Outer Layer (The Third Step of
Polymerization): Preparation of Latex 1HML
[0071] To thus obtained Latex 6HM, an initiator solution composed
of 200 ml of deionized water and 7.4 g of the polymerization
initiator (KPS) dissolved therein was added and then a monomer
mixture liquid composed of 311 g of styrene, 85 g of n-butyl
acrylate, 3.62 g of acrylic acid, 2.04 g of 2-hydroxyethylacrylate
and 10.4 g of n-octyl-3-mercaptopropionic acid ester was dropped to
the latex spending for 1 hour at a temperature condition of
80.degree. C. After completion of the dropping, the resulted liquid
was heated and stirred for 1 hour for polymerization (third step
polymerization), and then cooled by 28.degree. C. to obtain latex.
Thus obtained latex was referred to as Latex 1HML.
[0072] (2) Preparation of Colorant Dispersion 1
[0073] In 1,600 ml of deionized water, 90 g of the anionic
surfactant was dissolved by stirring. To the solution, 400.0 g of
C.I. Pigment Blue 15:3 was gradually added while stirring, and then
dispersed by the stirring apparatus CLEARMIX manufactured by M
Technique Co., Ltd. so as to obtain the colorant particles having
particle diameter of less than 200 nm, and dispersion of a colorant
was obtained. The dispersion was referred to as Colorant Dispersion
1.
[0074] (3) (CoagulationFusion) Preparation of Coagulated
Particles
[0075] Into a reaction vessel (four-mouth flask) to which a thermal
sensor, a cooling tube, a nitrogen gas introducing device and a
stirring device were attached, 200 g in terms of solid ingredient
of Latex 1HML, 3,000 g of deionized water and 33 g of Colorant
Dispersion 1 were charged. The inner temperature of the vessel was
adjusted to 30.degree. C. and then the pH value of the liquid was
adjusted to 8-11.0 by adding a 5 mol/L aqueous solution of sodium
hydroxide. After that, a solution composed of 20 ml of deionized
water and, dissolved therein, 20 g of magnesium chloride
hexahydrate was dropped to the above liquid spending for 10 minutes
at 30.degree. C. The liquid was stood for 3 minutes and then heated
up to 75.degree. C. spending 60 minutes.
[0076] Under such the conditions, the diameter of the associated
particle was measured by Coulter Counter MS-II, and an aqueous
solution composed of 60 ml of deionized water and, dissolved
therein, 29 g of sodium succinate was added at a time when the
number average diameter of the particles was attained at 6-7 .mu.m
to stop the growing the particles. Moreover, the fusion of the
particles was continued as a ripening treatment by heating and
stirring for 6 hours at 90.degree. C. After that temperature was
cooled down to 30.degree. C., pH was adjusted to 2.0 with
hydrochloric acid, then stirring was terminated. Thus formed
particles of salted out, coagulated and fused were filtrated and
washed repeatedly with deionized water at 45.degree. C. Colored
particles C1 was obtained by drying warm air at 40.degree. C.
(Preparation of Colored Particle C2)
[0077] (1) Preparation of Latex 2HML
[0078] 1) Preparation of Core Particle (The First Step of
Polymerization): Preparation of Latex 2H
[0079] In the preparation process of Latex 1H, a mixture of
monomers composed of 75.3 g of styrene, 16.7 g of n-butyl acrylate,
2.47 g of acrylic acid and 1.59 g of 2-hydroxyethylacrylate was
employed to obtain latex. The latex was referred to as Latex
1H.
[0080] 2) Formation of Intermediate Layer (Second Step of
Polymerization): Preparation of Latex 2HM
[0081] In the preparation process of Latex 1HM, Latex 2H was
employed in place of Latex 1H, and a monomer mixture composed of
101.2 g of styrene, 30.1 g of n-butyl acrylate, 3.52 g of acrylic
acid, and 2.27 g of 2-hydroxyethylacrylate was employed for the
polymerization. Thus latex referred to as Latex 2HM.
[0082] 3) Preparation of Outer Layer (The Third Step of
Polymerization): Preparation of Latex 2HML
[0083] In the preparation process of Latex 1HML, a monomer mixture
liquid composed of 299 g of styrene, 87 g of n-butyl acrylate, 10.3
q of acrylic acid, and 6.66 g of 2-hydroxyethylacrylate was
employed for the polymerization to obtain latex. Thus obtained
latex was referred to as Latex 2HML.
[0084] Colored Particle C2 was obtained by preparation of
associated particles employing Latex 2HML in place of Latex 1HML in
the preparation process of Colored Particle C1.
(Preparation of Colored Particle C3)
[0085] (1) Preparation of Latex 3HML
[0086] 1) Preparation of Core Particle (The First Step of
Polymerization): Preparation of Latex 3H
[0087] Latex was prepared employing a mixture of monomers composed
of 76.2 g of styrene, 17.1 g of n-butyl acrylate, 1.47 g of
methacrylic acid and 1.56 g of 2-hydroxyethylmethacrylate in the
preparation process of Latex 1H. The latex was referred to as Latex
3H.
[0088] 2) Formation of Intermediate Layer (Second Step of
Polymerization): Preparation of Latex 3HM
[0089] In the preparation process of Latex 1HM, Latex 3H was
employed in place of Latex 1H, and a monomer mixture composed of
103.4 g of styrene, 29.6 g of n-butyl acrylate, 2.10 g of
methacrylic acid, and 2.27 g of 2-hydroxyethylmethacrylate was
employed for the polymerization. Thus latex referred to as Latex
3HM.
[0090] 3) Preparation of Outer Layer (The third Step of
Polymerization): Preparation of Latex 3HML
[0091] In the preparation process of Latex 1HML, a monomer mixture
liquid composed of 302 g of styrene, 88 g of n-butyl acrylate, 6.19
g of methacrylic acid, and 6.55 g of 2-hydroxyethylmethacrylate was
employed for the polymerization to obtain latex. Thus obtained
latex was referred to as Latex 3HML.
[0092] Colored Particle C3 was obtained by preparation of
associated particles employing Latex 3HML in place of Latex 1HML in
the preparation process of Colored Particle C1.
(Preparation of Colored Particle C4)
[0093] (1) Preparation of Latex 4HML
[0094] 1) Preparation of core particle (The first step of
Polymerization): Preparation of Latex 4H
[0095] A latex was prepared employing a mixture of monomers
composed of 70.8 g of styrene, 17.6 g of n-butyl acrylate, 3.70 g
of methacrylic acid and 4.19 g of 2-hydroxyethylmethacrylate in the
preparation process of Latex 1H. The latex was referred to as Latex
4H.
[0096] 2) Formation of Intermediate Layer (Second Step of
Polymerization): Preparation of Latex 4HM
[0097] In the preparation process of Latex 1HM, Latex 4H was
employed in place of Latex 1H, and a monomer mixture composed of
94.3 g of styrene, 31.5 g of n-butyl acrylate, 5.25 g of
methacrylic acid, and 5.96 g of 2-hydroxyethylmethacrylate was
employed for the polymerization. Thus latex referred to as Latex
4HM.
[0098] 3) Preparation of Outer Layer (The third Step of
Polymerization): Preparation of Latex 4HML
[0099] In the preparation process of Latex 1HML, a monomer mixture
liquid composed of 283 g of styrene, 87 g of n-butyl acrylate, 15.5
g of methacrylic acid, and 17.5 g of 2-hydroxyethylmethacrylate was
employed for the polymerization to obtain latex. Thus obtained
latex was referred to as Latex 4HML.
[0100] Colored Particle C4 was obtained by preparation of
associated particles employing Latex 4HML in place of Latex 1HML in
the preparation process of Colored Particle C1.
(Preparation of Colored Particle C5)
[0101] (1) Preparation of Latex 5HML
[0102] 1) Preparation of Core Particle (The First Step of
Polymerization): Preparation of Latex 5H
[0103] A latex was prepared employing a mixture of monomers
composed of 80.3 g of styrene, 15.8 g of n-butyl acrylate, and 0.25
g of acrylic acid in the preparation process of Latex 1H. The latex
was referred to as Latex 5H.
[0104] 2) Formation of Intermediate Layer (Second Step of
Polymerization): Preparation of Latex 5HM
[0105] In the preparation process of Latex 1HM, Latex 5H was
employed in place of Latex 1H, and a monomer mixture composed of
107 g of styrene, 29.6 g of n-butyl acrylate, and 0.352 g of
acrylic acid was employed for the polymerization. Thus latex
referred to as Latex 5HM.
[0106] 3) Preparation of Outer Layer (The Third Step of
Polymerization): Preparation of Latex 5HML
[0107] In the preparation process of Latex 1HML, a monomer mixture
liquid composed of 315 g of styrene, 87 g of n-butyl acrylate, and
1.04 g of acrylic acid was employed for the polymerization to
obtain latex. Thus obtained latex was referred to as Latex
5HML.
[0108] Colored Particle C5 was obtained by preparation of
associated particles employing Latex 5HML in place of Latex 1HML in
the preparation process of Colored Particle C1.
(Preparation of Colored Particle C6)
[0109] (1) Preparation of Latex 6HML
[0110] 1) Preparation of Core Particle (The First Step of
Polymerization): Preparation of Latex 6H
[0111] A latex was prepared employing a mixture of monomers
composed of 72.0 g of styrene, 18.2 g of n-butyl acrylate, 4.95 g
of acrylic acid and 1.20 g of 2-hydroxyethylmethacrylate in the
preparation process of Latex 1H. The latex was referred to as Latex
6H.
[0112] 2) Formation of Intermediate Layer (Second Step of
Polymerization): Preparation of Latex 6HM
[0113] In the preparation process of Latex 1HM, Latex 6H was
employed in place of Latex 1H, and a monomer mixture composed of
96.1 g of styrene, 32.2 g of n-butyl acrylate, 7.05 g of acrylic
acid and 1.70 g of 2-hydroxyethylmethacrylate was employed for the
polymerization. Thus latex referred to as Latex 6HM.
[0114] 3) Preparation of Outer Layer (The Third Step of
Polymerization): Preparation of Latex 6HML
[0115] In the preparation process of Latex 1HML, a monomer mixture
liquid composed of 285 g of styrene, 92 g of n-butyl acrylate, 20.7
g of acrylic acid and 5.00 g of 2-hydroxyethylmethacrylate was
employed for the polymerization to obtain latex. Thus obtained
latex was referred to as Latex 6HML.
[0116] Colored Particle C6 was obtained by preparation of
associated particles employing Latex 6HML in place of Latex 1HML in
the preparation process of Colored Particle C1.
(Preparation of Colored Particle C7)
[0117] (1) Preparation of Latex 7HML
[0118] 1) Preparation of Core Particle (The First Step of
Polymerization): Preparation of Latex 7H
[0119] A latex was prepared employing a mixture of monomers
composed of 79.7 g of styrene, 15.6 g of n-butyl acrylate, 0.44 g
of methacrylic acid and 0.64 g of 2-hydroxyethylmethacrylate in the
preparation process of Latex 1H. The latex was referred to as Latex
7H.
[0120] 2) Formation of Intermediate Layer (Second Step of
Polymerization): Preparation of Latex 7HM
[0121] In the preparation process of Latex 1HM, Latex 7H was
employed in place of Latex 1H, and a monomer mixture composed of
106 g of styrene, 29.3 g of n-butyl acrylate, 0.63 g of methacrylic
acid and 0.92 g of 2-hydroxyethylmethacrylate was employed for the
polymerization. Thus latex referred to as Latex 7HM.
[0122] 3) Preparation of Outer Layer (The Third Step of
Polymerization): Preparation of Latex 7HML
[0123] In the preparation process of Latex 1HML, a monomer mixture
liquid composed of 312 g of styrene, 86 g of n-butyl acrylate, 1.86
g of methacrylic acid and 2.69 g of 2-hydroxyethylmethacrylate was
employed for the polymerization to obtain latex. Thus obtained
latex was referred to as Latex 7HML.
[0124] Colored Particle C7 was obtained by preparation of
associated particles employing Latex 7HML in place of Latex 1HML in
the preparation process of Colored Particle C1.
(Preparation of Colored Particle C8)
[0125] (1) Preparation of Latex 8HML
[0126] 1) Preparation of Core Particle (The First Step of
Polymerization): Preparation of Latex 87H
[0127] A latex was prepared employing a mixture of monomers
composed of 58.7 g of styrene, 16.9 g of n-butyl acrylate, 7.40 g
of methacrylic acid and 19.1 g of 2-hydroxyethylmethacrylate in the
preparation process of Latex 1H. The latex was referred to as Latex
8H.
[0128] 2) Formation of Intermediate Layer (Second Step of
Polymerization): Preparation of Latex 8HM
[0129] In the preparation process of Latex 1HM, Latex 8H was
employed in place of Latex 1H, and a monomer mixture composed of
76.3 g of styrene, 31.2 g of n-butyl acrylate, 10.5 g of
methacrylic acid and 19.1 g of 2-hydroxyethylmethacrylate was
employed for the polymerization. Thus latex referred to as Latex
8HM.
[0130] 3) Preparation of Outer Layer (The third Step of
Polymerization): Preparation of Latex 8HML
[0131] In the preparation process of Latex 1HML, a monomer mixture
liquid composed of 224 g of styrene, 91.5 g of n-butyl acrylate,
30.9 g of methacrylic acid and 56.1 g of 2-hydroxyethylmethacrylate
was employed for the polymerization to obtain latex. Thus obtained
latex was referred to as Latex 8HML.
[0132] Colored Particle C7 was obtained by preparation of
associated particles employing Latex 7HML in place of Latex 1HML in
the preparation process of Colored Particle C1.
[0133] (Acid Value and Hydroxyl Group Value of Binder Resin)
[0134] The acid value and the hydroxyl group value of the binder
resin were measured in accordance with JIS K-0070. Provided that
tetrahydrofuran was used as the solvent because the resin cannot be
solved by the mixture of diethyl ether and ethanol designated in
JIS. A potentiometric titration method was used since the end point
was made unclear sometimes by coloring of the solution in the
neutralization titration using an indicator. Measured results are
shown in Table 1.
TABLE-US-00001 TABLE 1 Hydroxyl Hydroxyl group group value/Acid
Binder resin Acid value value value Remarks Latex 1 HML 7 2.45 0.35
Inventive Latex 2 HML 20 8 0.4 Inventive Latex 3 HML 10 7 0.7
Inventive Latex 4 HML 25 18.75 0.75 Inventive Latex 5 HML 2 0.4 0.2
Comparative Latex 6 HML 40 6 0.15 Comparative Latex 7 HML 3 2.88
0.96 Comparative Latex 8 HML 50 60 1.2 Comparative
[0135] <<Preparation of Developers C1 to C8>>
[0136] To each of the above prepared Colored Particles C1 to C8,
1.0% by weight of hydrophobic silica TG-811F, manufactured by
Cabosil Co., Ltd., 1.5% by weight of strontium titanate particles
and 1.0% by weight of NX90, manufactured by Nihon Aerosil Co.,
Ltd., were added and mixed by Henschel mixer, manufactured by
Mitsui Mining Co., Ltd. Then coarse particles were removed from the
resultant mixture by a sieve having an opening size of 45 .mu.m.
Thus Developers C1 to C8 ere prepared.
[0137] (Softening Point)
[0138] The softening point of the developer is a value measured by
a flow tester. Concretely, Flow Tester CFT-500, manufactured by
Shimadzu Seisakusho Co., Ltd., was used under the conditions of a
fine hole diameter of the die of 1 mm and a length of 1 mm, a load
of 1.96.times.10.sup.6 Pa and a temperature rising rate of
6.degree. C./min. One cubic centimeter of sample was melted and
flown out and the softening point was determined by the temperature
corresponding to 1/2 point between the temperature at the beginning
of flowing and that at the ending of flowing.
Evaluation
[0139] The fixing ability and the durability of the developer were
evaluated by using a color laser printer MAGICOLOR 2300DL,
manufactured by Konica Minolta Business Technologies Co., Ltd.,
which separately had the transferring mechanism and the fixing
mechanism.
[0140] (Fixing Ability; Non Off-Set Temperature Range)
[0141] The test machine was modified so that the fixing temperature
of the fixing apparatus can be optionally varied. A solid image
formed by three colors (Y, M and C) in a total amount of 15
g/m.sup.2 was printed for determined the lower limit of temperature
at which the off-set is not caused. For determining the upper limit
temperature at which the off-set is not caused, mono-color
gradation images of each color developers in an amount of 0 to 5.0
g/m.sup.2 were printed. The evaluation was carried out according to
the range of the temperature in which the low temperature off-set
and high temperature off-set are not caused on any of the images
(non off-set temperature range). Standard CF paper for CF900 having
a weight of 80 g/m.sup.2 was used for the test. Samples on which
the off-set was slightly observed were judged as inferior.
[0142] A: The non off-set temperature range was not less than
40.degree. C.
[0143] B: The non off-set temperature range was not less than
30.degree. C. and less than 40.degree. C.
[0144] C: The non off-set temperature range was less than
30.degree. C.
[0145] (Low Temperature Fixing Ability; Folding Test)
[0146] The image formed and fixed at 130.degree. C. by the above
testing condition for evaluating the non off-set temperature range
was folded at the middle portion of the image and peeling off of
the image was visually observed.
[0147] A: No peeling off was observed on the image.
[0148] B: The peeling off was caused some degree but acceptable for
practical use.
[0149] C: The peeling off was considerably caused, some problems
were caused for practical use.
[0150] (Durability; Mechanical Stability)
[0151] The durability test was carried out by 2,000 times of
printing operation using white paper without image formation, and
then the tested developer was take out and observed by a reflection
microscope at a magnitude of 1,000 times and for 5 observing fields
and number of crushed particles per 500 particles of the developer
was counted. The evaluation norms were as follows.
[0152] A: No crushed particle was observed, acceptable for
practical use.
[0153] B: One to 9 crushed particles were observed but acceptable
for practical use.
[0154] C: Ten or more crushed particles were observed, some
problems were caused for practical use.
TABLE-US-00002 TABLE 2 Low Softening temperature point Fixing
fixing Developer Binder resin (.degree. C.) ability ability
Durability Remarks C1 Latex 1 HLM 110 A A A Inv. C2 Latex 2 HML 115
A A A Inv. C3 Latex 3 HML 113 A A A Inv. C4 Latex 4 HML 116 A A A
Inv. C5 Latex 5 HML 110 C B C Comp. C6 Latex 6 HML 117 B C B Comp.
C7 Latex 7 HML 113 C C C Comp. C8 Latex 8 HML 120 A C A Comp. Inv.:
Inventive, Comp.: Comparative
[0155] It is understood from Table 2 that Developers C1 to C4 using
the resin according to the invention are superior to the
comparative Develpers C5 to C8 in the all evaluation items of the
fixing ability, low temperature fixing ability and durability.
* * * * *